1. Field of the Invention
The present invention relates to an apparatus for a discharge treatment and a method for the discharge treatment.
2. Description of the Related Art
In a corona discharge treatment, an electric discharge is induced by applying an AC (alternating current)-high voltage between paired electrodes, composed of a roll or plane standard electrode and a corona electrode spaced opposite thereto, and an article placed between the paired electrodes is treated with the electric discharge. However, the corona discharge treatment has the following defects:
(a) In some cases an article may be damaged by repeated discharge treatments. For example, an article made of a thermoplastic resin may be melted. Such a melting occurs when an AC-high voltage having a high-frequency is applied.
(b) When the AC-high voltage applied is a sinusoidal wave, the resultant electric discharge might be concentrated, and thus, an article treated could be badly damaged, for example, pinholes could be produced therein.
Further, if the corona discharge treatment is industrially utilized, the ability to conduct a high-speed discharge treatment is required. Conceivably, a method for a high-speed discharge treatment can be realized by increasing the discharging energy density per unit area of an electrode. Nevertheless, even under usual conditions, a treated article may be damaged, for example, melted, or pinholes may be produced, as mentioned above. It is difficult to carry out the corona discharge treatment under the high density of the discharging energy, as the conditions occur under which the article is easily melted or pinholes are easily produced.
Furthermore, it is known that the surface of an article can be roughened by the corona discharge treatment, but a roughening treatment which can be industrially utilized is not known.
The inventors of the present invention made an intensive investigation into a solution to the above problems, and as a result found that, by passing gas at a rate of 10 m/sec or more through a space formed between a pair of electrodes, the temperature of the article to be treated, and ambient temperature, can be lowered, the electric discharge can be homogenized, i.e., the concentration of the electric discharge can be reduced, an increase of the discharge energy density does not damage the article to be treated, a high-speed discharge treatment can be stably carried out, and the article surface can be roughened under a high density of the discharging energy. Further, the inventors also found that, because the density of the discharging energy can be raised, a means for inducing an electric discharge can be miniaturized.
The present invention is based on the above findings.
Accordingly, the object of the present invention is to provide a discharge treatment apparatus and a discharge treatment method which enable a high-speed discharge treatment and roughening treatment without damaging the article.
Other objects and advantages will be apparent from the following description.
In accordance with the present invention, there is provided an apparatus for a discharge treatment, comprising
a pair of electrodes located opposite to each other;
a means for applying an alternating current-high voltage between the electrodes; and
a means for passing a gas mainly composed of air at a rate of 10 m/sec or more through a space formed between the electrodes.
A preferable apparatus of the present invention has a means for applying the alternating current-high voltage having a pulse wave pattern between the electrodes.
Another preferable apparatus of the present invention has a means for passing a gas mainly composed of air at a rate of 85 m/sec or more through the space formed between the electrodes.
In accordance with the present invention, there is also provided a process for a discharge treatment of an article, comprising applying an alternating current-high voltage between a pair of electrodes located opposite to each other, to the article placed between the electrodes, while a gas mainly composed of air is passed at a rate of 10 m/sec or more through a space formed between the electrodes, to thereby expose the article to an electric discharge induced between the electrodes.
In a preferable process of the present invention, the alternating current-high voltage applied is a pulse wave.
In another preferable process of the present invention, the gas mainly composed of air is passed at a rate of 85 m/sec or more through the space formed between the electrodes.